Ohmic heating is a concept of product heating that uses the electrical resistance of the material itself to produce heat

1. Recent Studies and Prospect
Application of Ohmic Heating for
Fermentation Process: A Mini-Review
Diang Sagita, Doddy A.
Darmajana, Dadang D. Hidayat
Research Center for Appropriate
Technology
Indonesian Institute of Sciences

2. INTRODUCTIO
N
Fermentation is one of
the oldest food
processing techniques
Fermentation
1
Fermentation serves a variety of purposes
such as:
(a)Food preservation
(b)Providing attractive taste and additional
nutritional value to many products
(c) Enhancing food safety by removing
natural toxins and compounds that
aren't required in the product
(d)Preventing the growth of disease-
causing microbes

3. INTRODUCTIO
N
Traditional fermentation
usually takes a long
time and difficult to
achieve optimum
temperatures condition.
Traditional
Fermentation
2
Temperature is one operating variable that has
an effect on the quality of the fermentation
process. The microbes that may be involved
include molds (mycelial fungi), yeasts
(unicellular fungi), and bacteria will develop to
their full potential if the ideal conditions and
temperatures are set and maintained during
the fermentation process.

4. INTRODUCTIO
N
Conventional fermenter
that utilize heat transfer
by conduction and
convection have not
been able to
homogenize the
temperature
Conventional
Fermenter
3
Illustration of heat transfer by conduction and convection
Processed product
Heat Source

5. Ohmic Heating
Technology
The use of ohmic technology can save
energy from 82 to 97% while reducing
heating time by 90-95% compared to
conventional heating
A promising technology that produces rapid
and uniform heating has continuously
investigated by many researchers
Its names is derived from Ohm's law
The aims of this study:
To present a mini-review which
describes several scientific studies
related to the application of ohmic
heating for the fermentation processes
and its potential for further research and
development

6. Ohmic Heating
Principles
The principle scheme of ohmic heating technology
Ohmic heating is a concept of product
heating that uses the electrical resistance
of the material itself to produce heat
01. Electrical conductivity (EC)
03. EC of various materials especially fruit concentrate
(apples, pineapples, pears, strawberries, and peaches):
range from 0.05 to 1.2 S/m (Siemens per meter).
Pure water has poor electric conductivity, and it is around
0.0055 mS/m
02. Electrical conductivity (σ) is a unit that indicates how
well a material transmits electric current movements
Main
Factor

7. Ohmic heating
design and
parameters
1. Electrical conductivity (S/m): The higher the EC value the faster the heating
2. Voltage gradient (V/cm): The heating rate increases as the voltage gradient increases,
then along with the increase in temperature, the EC will also increase
3. Frequency and waveform : Low frequency and sawtooth wave may give a higher
heating rates and yields than high frequency and sine wave
4. Electrode : Electrodes are typically selected based on price and functionality (resistance
and durability)
5. Chamber/container: Plastic, ceramic, glass or something similar (isolator) that cannot
transmit electricity is strongly recommended for the ohmic container
6. Control system : This feature has the function to control the temperature and electric
current

8. Ohmic heating effect
and efficiency
Ohmic heating is used for
preheating, pasteurization
and sterilization of products
such as milk, fruit juice even
sausages
Sakr and Liu (2014)
Energy efficiency for
pasteurizing mango juice
up to 94% and time
required to reach 80oC =
130 s
Adilaksono et al.
(2014) Ohmic heating had been
proven to reduce less the
loss of carotenoid
compounds during
heating compared to
conventional heating
Achir et al. (2016)
Ohmic heating does not
statistically change the
chemical composition of
sausages, pH, lipid
oxidation
Inmanee et al. (2019)
Ohmic heating was
suitable to sterilize
highly viscous products
and also better energy
efficiency
Cho et al. (2017)
ohmic heating
efficiency reach 94.2%
while microwave
heating only 24.7%
Nguyen et al. (2013)
Previously Published Paper

9. Determination of
the energy efficiency
Energy efficiency was defined as the ratio between the
energy used for heating the material with the input of
electrical energy
Where, η is energy efficiency (%), m is mass of the
heated material (kg), cp is specific heat of material
(kJ/kgoC), Tf is the final temperature (oC), Ti is the initial
temperature (oC) dan Δt is heating time (s)

10. Ohmic heating
application for
fermentation process
Previously published papers have been reported on the application of ohmic
heating technology in the fermentation process
Sources Product Purpose
Reta et al. (2017a) Robusta Coffee Evaluation of the flavour characteristics of coffee produced by
produced by Ohmic fermentation technology
Reta et al. (2017b) Arabica Coffee Effect of ohmic heating on the acidity of Arabica coffee
Risqan et al. (2017) Cocoa Application of ohmic fermentation technology on the cocoa
cocoa bean
Muhidong and Mustafa
(2020)
Arabica Coffee Evaluation of sensory and cupping score of coffee produced
produced by ohmic heating technology
Supratomo et al. (2019)
(2019)
Cocoa Design and performance test of ohmic assisted fermentation
fermentation apparatus for cocoa fermentation
Sagita et al. (2020) Soybean Preliminary test of the use of ohmic heating on soybean (for
(for tempeh), design and test of ohmic based fermenter
model

11. Ohmic heating
application for
fermentation process
1
The flavor profile of Robusta coffee derived from
Bantaeng fermented with Ohmic fermentation
technology is categorized as excellent specialty
coffee, with a total score of 83.75
Robusta Coffee
Treatment of 18 hours fermentation time at a
temperature of 35°C
Reta et al. (2017a)

12. Ohmic heating
application for
fermentation process
2
Ohmic technology has a good impact on the fermented Arabica
coffee result. This technology provides fermented coffee, which
has a much lower total acidity of 0.18% compared to traditional
fermentation
Arabica Coffee
Treatment of 18 hours fermentation time at a temperature of
30°C
Muhindong and Mustafa (2020)
Reta et al. (2017b)
It is reported that ohmic-assisted fermentation could gain a
cupping score ranging from 81.81 to 85.25 with an average
cupping score of 84.03. Furthermore, the application of 12
hours and 35 °C temperature generated the highest cupping
score of 85.25.

13. Ohmic heating
application for
fermentation process
3
Ohmic fermentation for 3 days at 50 °C did not show a significant
difference with the results of 5-day fermentation in traditionally.
Cocoa
Risqan et al. (2017)
It is reported that the use of an ohmic fermenter can speed up the
fermentation time where the fermented beans yield by 95% can
be achieved in just 3 days (using 40, 45 and 50 °C) using the
ohmic fermenter, while conventionally need about 5 days.
Supratomo et al. (2019)
This phenomenon occurs because ohmic heating will help to shorten the microbial
lag phase in the early stages of fermentation by providing the proper temperature
for yeast growth

14. The use of ohmic technology has been demonstrated to be applicable to a variety of fermentation processes in
terms of temperature conditioning to achieve optimal and regulated conditions.
Name of product Major ingredient Functional microorganism
Quark Cows' milk Lactic acid bacteria (LAB)
Yogurt Cows' milk LAB
Sauerkraut White cabbage LAB
Cultured milk ("karnemelk") Cows' milk LAB
Treated black olives Olives LAB
Gouda cheese Cows' milk LAB
Raw fermented sausages Beef meat LAB
Yeast-leavened bread Wheat flour Yeasts (Y)
Gruyere cheese Cows' milk LAB + propionibacteria
Pumpernickel bread Rye flour LAB + Y
Mixed sourdough bread Rye + wheat flour LAB + Y
Camembert cheese Cows' milk LAB + molds
Soy sauce Soybeans and wheat Molds + LAB + Y
Tempeh Soybeans LAB + molds + Y
Nata de coco Coconut water Acetobacter xylinum
Fermented cassava (“peuyeum”) Cassava Y
Fermented cocoa bean Cocoa beans LAB / Y
Fermented coffee bean Coffee beans LAB / Y
Prospect and potential
development of ohmic-based
fermenter
Some products that involve a fermentation process (Adams and Nout, 2001)

15. Conclusion
1. There is an effect of using ohmic heating in the fermentation
process and has a positive impact on the results of fermented
products
2. More research into the phenomena and reactions that occur during
fermentation using ohmic heating is needed to be studied,
especially on products that are commonly fermented
3. Since it produces a high uniformity of temperature distribution for
liquid and non-liquid products, the ohmic heating system has been
proven to be important and appropriate for the construction of
fermenter equipment

16. THANK YOU
Do you have any
questions?
diang.sagita@lipi.go.id
+62 857 1900 2251